Process for producing gas currents carrying predetermined quantities of nitrogen trichloride



July '14, 1942*; A, KLEUN I l 2,289,436 PRocEss Fon PnoDucING A GASCURRENT CARRYING; PREms'rrzlmnuany QUANTITY 0F NITROGEN TRICHLORIDEFi1ed Ju1y 18, *1939" Adrianus .Kleyn b,

A Patented CARRYING ornlraocmrlcmm zAdrianus1r1i.-m, noun-cani, AnnaritaJuiy 1s. m9, serai :sarcasm s Vcumivfrrrnrs -rnnenecnerlmmomber 11, 193s1 2 claims. (ci. sparsi' The present invention relates to the productionof gas currents carrying halogenated nitrogen 'compounds as, forexample, nitrogen trichloride and has for an object to provide animproved' process which can be economically and eiectively operated byrelatively Vuntrained persons. Nitrogen trlchloride is used commerciallyfor bleaching and for improving thebakingl quality' of wheat and ryeiiour. Themanner of use is of such character that it is important thatthe rate of production be closely controlled.l Y

The maintenance of a supply of the material in use `oiTers considerable`diillculty under the 4usual commerc al conditions. Ordinarily' it 'isproduced as where used and its production must be carried on by suchemployees as are available in the -V establishment where skilledchemists are not available. t

One method of preparation consists of introiducing chlorine gas into asolution of ammonium chloride. fI'his method is subject to the dangersattendantI upon the handling of the chlorine by a solution by a 'currentof gas. Vf'lhe present invention provides a process in which solid.oxidizing agents comprising amongst others hypochlovrites are caused toreact with an acid solution 5 containing ammonium ions and chlorine ionswhilst passing a gas current through said so1u' tion. lSaid process canbe carried out togreatl advantage on a commercial scale to produce a gascurrent containing nitrogen trichloride at a rate adjusted to therequirements of use and is one that can be operated and controlledeffectively to produce desired results by the operatives ordinarilyavailable in the plants where the product is used. Y

The 4invention has been developed in the working out of a processwherein an oxidizing agent in granular or pulverized yform is added toan `acid solution containing ammonium chloride,and for the Purposes ofdisclosure of the principles of the invention such a process will bemore particularly described but it will be understood thatthe particulardescription ls illustrative operatives not' particularly skilled in thisclass of merely and is not intended as Vdening the'limits worlr. IAlso.chlorine must be transported insteel of the invention. v cylinders withthe attendant considerable trans'- 25 The close control of theproduction is accomportationl costs including the return transportationof the empty cylinders.

In the production oi' the nltrogengtrichloride v, at a substantiallyconstant rate 'to meet the ref t quirements o! use, it is necessarytointroducethe chlorine into the 'reaction retorts at avpredeterminedand carefully regulated -rate and this requires complicated and costlyapparatus.

Electrolytic methods of producing nitrogen trichloride havebeen proposedbut thisA involves the expense and inconvenience of special equipmentand requires operatives capable 'of handling the electrolytic processunder vaconditions requiring constant supervision `in order to maintainthe production Withinthe relativelyl narrow limits 40 required in use.In -both casesthe nitrogen chloride must not be allowed to accumulatebut must Abe carried off by a current of air or inert gas in order to beused 'as a bleachingagent.

vThe diiliculties of the Ypresent practice are th greater wherecontinuous'day and night operation is necessary.

-It is known that nitrogen trichloride can be prepared by lreacting ahypochlorite for a con- NCI: has been based on said reaction. It is alsoknown to remove nitrogen trichloride formed in 55 rents.

plished in the process oi?v the present invention by controlling therate of addition of the oxidizing agent to the reaction mixture.Conveniently, the oxidizing agent is used in granular, preferablypulverized'form and is added substantially l continuously at apredetermined rate, for. example in a' rapid succession of smalldosesfwhile f the acidity. an'd the content vof ammonium ions f and ofchlorine ions in the reaction mixture are maintained within thenecessarylimits. Chlorine ionsfforgthe reaction may be supplied with orasa component part of the oxidizing agent or may be separately suppliedto the bath with ammonium ions.

In the accompanying drawing forminga part hereof there is shownconventionally an .apparatus for use in operating the process.

'The -iigure isa diagrammatic `sectional view of an apparatus for use inpracticing the invention.

The tank I is shown as divided by a partition 2 depending from the cover4 to a point Well vbelow the level of the liquid but not extending tothe bottom of the tank` to provide two gas cham- '50 bers A and B abovethe level of the liquid.

A discharge outlet 3v is provided at the bottom of the tank and acharging aperture 5 is provided in the cover. An upstanding iiange 5laround the aperture inhibits undesired air cur- A *charging device 6 isprovided to facilitate the gradual additionl of measured charges ofgranular material. By this charging device successive charges ofgranular oxidizing agent can be added at predetermined intervals.Furthermore the operation voi! this charging device isl such that thematerial may be added at a rate substantially corresponding to the rateof reaction in the reaction tank. The charging device shown in PatentNo. 1,925,650 is particularly suitable. A

An air conduit I leadsl from the' chain'bcijA above the reaction liquidto the suction side of a blower 8 which forces a constant currenty ofair through the conduit 9 to a distributing head 9' The current of airYin through the opening 5 and chlorine ions are brought into the Vbath bythe oxidising agent, it is also necessary to maintain the requiredcontent of chlorine ions by suitable additions. The acidity required inthe bath decumulates at the bottom of the container may be y removedthrough the outlet 3.

well below the liquid level in the chamber B.

from the chamber A eiectively prevents escape' of ,vapour or gascollecting above the liquidina.I

chamber A and the flow of air through the reaction mixture preventsexcessive concentration ci the volatile product of the reaction withinthe solution. A discharge conduit l carries the air charged withnitrogen trichloride to the point ci l use. During operation the airpressure in chamber B will cause a difference oi level of the reactionmixture.

A bracket on the cover carries a stirring device I2. The charge feedingdevice 6 and the stirrer I2 are connected to be driven when the blower 8is operated. The blower may be driven by an electric motor,v not shown,and pulleys i4 and I5 of the charging device and the stirrer may beconnected to be driven from the blower as by belt gearing conventionallyindicated at |3, |3I, |32, |33, |34. By this arrangement the feed of-material in the device 6 always stops when the air currentisdiscontinued.

tion mixturey consisting'of an acidiiled aqueous' solution of ammoniumchloride.

If bleachingpowder is used as oxidising agent the solution may containe. g; about 2% ammoniumchloride and about 5% sulphuric acid. Instead ofordinary bleaching powder preferably a product with a higher content ofcalcium hypolquantity such as will provide the formation of nitrogentrichloride 'at the rate desired. The reaction mul proceeds according tothe reaction for- In'opera'tion the tankis charged with a reac- Thereaction may be carried on at room temperature. Preferably thetemperature is within the range 10 to 30 C. Nitrogen trichloride isformed very readily and at a rate deiinitely determined by the rate atwhich the oxidising agent is added to the vreaction mixture. This is .animportant feature of lthe process and one which makes it well adapted tobleaching operations.

The nitrogen trichloride formed according to the above described processis rapidly and continually removed from the reaction liquid by a gascurrent e. g. an air current so that the concentration of nitrogentrichloride in the reaction liquid cannot reach a dangerous limit. Atthe same time a decomposition of the nitrogen trichloride inthe reactionliquid is prevented so that the discharge of the nitrogen trichloride yfrom the liquid and the addition thereof to the our remains'i'nproportion to -the charging of the oxidising agent;

If the gas current is as uniform as the dosed delivery of the oxidisingagent to the reaction liquid it will always containv a uniform contentof NCls.

It isl advantageous to combine the charging device as shown in thedrawing in such a way to the device which causes the air current, forexample to the blower, that'when this device stops the charging devicealso stops in order to avoid the danger of a toohigh concentration ofnitroalso other solid oxidising agents may be used which are capable ofproducing chlorine in a solution of hydrochloric acid, such as M1102,PbOz etc.

Oxidising agents in granular form are pre- The ammonium ions and theacid consumed by the reaction must be restored to the bath from time totime or continually. If no sufcient gen trichloride in the reactionliquid. This mayV be obtained by driving the charging device from theshaft of the blower or by the same driving gear as the blower. Thisarrangement Provides also a relation of the amount of charged agent tothe volume of gas that passes through the blower and at a deiinite speedof the blower provides also a substantially constant percentage ofnitrogen trichloride in the gas.

The particular description 'illustrates a preferred manner of practicingthe invention, but it will be understood that variations may readily beintroduced by the chemist without departing from the scope of theinvention. For example instead of sulphuric acid it is possible to use'hydrochloric acid, especially if instead of calciumhypochlorite anoxidising agent is used that does not contain chlorine such as MnOz,thermore, it will be understood that the process 'is applicable to theproduction of other com- .pounds than that particularly described, such,

ior'example, as other halogenated nitrogen compounds.

The acidity and the content of ammonium chloride can be readilymaintained within the effective operating limits by adding suitable in-Furthe ingredients combined are suiciently stable when so handled. 4

It is a feature of the process that both the oxidising agent and. theammonium chloride are harmless and easily handled and the process doesnot constitute a hazard when operated by the type of operativesavailable in the plants where the nitrogen trichloride is used.

Reference shouldV be had to copending application, Serial No. 285,085filed concurrently herewith.v

What I claim is: s

1. The process for producing nitrogen trichloride at a predeterminedrate which comprises maintaining in a reaction bath a content ofammonium chloride of about 2%, a content of sulphuic acid of about 5%and adding thereto substantially continually at a predetermined rate agranular oxidising agent chiefly consisting of Vcalciumhyprochlorite andpassing a current of gas through the bath to remove nitrogen tlichlotride. v c

2. The process for charging a gas current with a predetermined quantityof nitrogen trichloride substantiallyfree from lchlorine which comprisesadding substantially continuously at a predeter- A mined rate a granularoxidising agent consisting chiefly of a hypochlorite to ammoniumchloride in acid aqueous solution having a pH value below 4.4 andperiodically adding ammonium chloride and acid to replace the ammoniumchloride 'con- ADRIANUS Kimm.

